chore: consolidate platform split checks

tests/db_isolation.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from collections.abc import Iterator
+from contextlib import contextmanager
+
+from govoplan_core.db.session import DatabaseHandle, configure_database, get_database, reset_database, set_database
+
+
+@contextmanager
+def temporary_database(database_url: str) -> Iterator[DatabaseHandle]:
+    try:
+        previous_database = get_database()
+    except RuntimeError:
+        previous_database = None
+
+    database = configure_database(database_url)
+    should_dispose = database is not previous_database
+    try:
+        yield database
+    finally:
+        if should_dispose:
+            database.engine.dispose()
+        if previous_database is None:
+            reset_database()
+        else:
+            set_database(previous_database)